Implosion-resistant cathode-ray tube and method of making



July 7, 1970 3,519,161

IMPLOSION-RESISTANT CATHODE-RAY TUBE AND METHOD OF MAKING Filed Aug. 14, 1968 a Sheets-Sheet 1 INVENTORS Zap/4 ,E/ Q zuz BY5U17DAJ 4). I 4??? 5} i770 MI/f July 7, 1910 D. PWELL ET 3,519,161

IMPLOSION--RESISTANT CATHODE-RAY TUBE AND METHOD OF MAKING Filed Aug. 14, 19 68 2 Sheets-Sheet 2 United States Patent O US. Cl. 220-2.1 9 Claims ABSTRACT OF THE DISCLOSURE A direct-viewing implosion-resistant cathode-ray television picture tube comprising a glass envelope having a funnel portion and a flanged faceplate portion. An annular reinforcing member comprising at least one strand of metallic wire is closely fitted around the external surface of the faceplate flange disposed either within a circumferential recess or in partially embedded relation. The reinforcing strand is sealed to the exterior surface of the faceplate flange either by a layer of low melting solder glass or by direct glass-to-metal sealing. A protuberance is also formed at the faceplate mold match line at a region of substantially maximum cross-sectional dimensions of the tube to provide an annular restraining recess for the reinforcing wire.

BACKGROUND OF THE INVENTION The present invention relates to cathode-ray tubes and more particularly to the control and prevention of fracture and implosive-explosive effects in vacuumized cathode-ray picture tubes for television reception. More specifically, this invention relates to improved types of direct-viewing cathode-ray image tubes having essentially all-glass envelopes and methods of fabricating such envelopes to eliminate breakage and to control sudden spontaneous devacuation thereof, either in processing, shipping, installation or while in service.

Cathode-ray tubes are vacuumized to very low pressure and breakage of the envelope for any reason may result in an implosion. Such implosion is accompanied by an explosion which, particularly in the case of impacted large-size envelopes, can be damaging where fragments of the envelope are projected in random directions with considerable force. The most common solution to this problem for many years has involved the use of a transparent tempered-glass implosion panel mounted in front of the television receiver cabinet and the cabinet itself has been relied upon to contain implosion-explosion effects. In more recent years, the television industry has adopted a safe direct-viewing tube envelope and it is this type of tube structure with which the present invention is concerned.

U.S. Pats. Nos. 3,220,592 and 3,220,593, both of which issued in our names on Nov. 30, 1965, relate to a basic type of direct-viewing, implosion-resistant, cathode-ray, television picture tube having a glass envelope and method of fabricating such tube envelope for its proper reinforcement. These inventions eliminate sources of fracture originating in or progressing into highly-stressed areas, particularly those of substantially maximum cross-sectional dimensions-of the envelope, and prevent the deleterious effects which result from sudden violent devacuation. As disclosed in the reference patents, noteworthy results have been achieved in protecting non-viewing areas of the tube envelope in such a manner that damage to the tube envelope from whatever source and wherever caused cannot result in damaging implosion-explosion. The need for a separate implosion plate, either mounted separately from or integrally with the image tube faceplate has been 3,519,161 Patented July 7, 1970 eliminated in such a manner that the tube faceplate may be a direct-viewing type in all conventional sizes of television picture tubes. Also, our US. Pats. Nos. 3,382,999 and 3,383,000, both issued May 14, 1968, disclose and claim further improvements in the field of reinforcing cathode-ray picture tubes to eliminate implosive effects due to off-center impact of the tube causing a neck-off at the tube small end which can occur at the beam gun tubulation. Also, our co-pending application, Ser. No. 553,757, filed May 31, 1966, now Pat. No. 3,403,805, discloses and claims a further improvement in the field of reinforcing cathode-ray image tubes.

Accordingly, the present invention constitutes an improvement over the tube constructions and methods of fabricating disclosed in the referenced patents and copending application, particularly with regard to further reducing the likelihood of an impulsion and preventing its occurrence, as well as providing improved reinforcement at minimal cost.

Therefore, it is an object of the present invention to provide a direct-viewing cathode-ray tube construction which is capable of convenient and expeditious fabrication to provide both resistance to fracture and control of sudden devacuation without serious fragmentation of the envelope under widely-varying adverse conditions.

Another object of this invention is to provide an improved type of essentially all-glass cathode-ray tube envelope by the use of a minimum of annular reinforcing elements mounted on non-viewing exterior surfaces of the envelope at a peripheral sidewall or rim area which is subject to damage due to its maximum cross-sectional dimensions with such elements controlling sudden devacuation upon fracture, however caused.

Another object of this invention is to provide a directviewing, non-imploding, cathode-ray image tube construction which may be directly viewed without a protective implosion panel mounted forwardly of its viewing area, such construction being applicable to resisting common forms of glass surface damage in both large and small size tubes and preventing their sudden devacuation, the internal working components of the completed tube being capable of functioning in their normal manner.

A further object of this invention is to provide a cathode-ray tube structure having an essentially all-glass tube envelope with at least one annular strand of metallic wire or narrow band in the form of an endless reinforcing loop surrounding the forwardmost non-viewing sidewalls immediately adjacent its viewing screen, said annular strand being sealed to the exterior glass surface therebeneath, either by direct glass-to-metal fusion or by an intermediate layer of low-melting solder glass, both the annular strand and solder glass sealant having coeflicients of thermal expansion complemental to the glass faceplate member, said reinforcing strand being adapted to mounting on either round or rectangular envelopes, either before or after their final fabrication into completed tubes.

A still further object of this invention is to provide a method of imparting fracture resistance to both round and rectangular glass cathode-ray tube envelopes to eliminate implosive-explosive effects on breakage of the envelope from any cause. Fracture propagation through an annular area of the faceplate rim portion and particularly at its maximum cross-sectional dimensions is prevented or retarded in such manner that violent uncontrolled collapse of major sidewalls of the envelope cannot occur.

The specific nature of this invention, as well as other objects and advantages thereof, will become apparent to those skilled in the art from the following detailed description taken in conjunction with the annexed sheets of drawings on which, by way of preferred example only, are illustrated the preferred embodiments of the invention.

On the accompanying drawings: FIG. 1 is a perspective view of a cathode-ray television picture tube fabricated in accordance with the present invention.

FIG. 2 is an enlarged fragmentary vertical sectional view of one sidewall portion of the tube envelope taken along the line 2-2 of FIG. 1.

FIG. 3 is a view similar to FIG. 2, taken along the line 33 of FIG. 1 at the corner region of the tube envelope.

FIG. 4 is a view similar to FIG. 2 showing another embodiment of the invention.

FIG. 5 is a similar view showing still another embodiment of the invention.

FIG. 6 is a similar view showing yet another embodiment of the invention.

The present invention is described hereinafter as specifically applied to the manufacture of cathode-ray television picture tubes. However, it will be apparent to those skilled in the art that the invention is equally applicable to the manufacture of many different types of vacuum tubes utilizing glass envolopes such as electrical discharge devices, particularly those having substantial dimensions which, due to atmospheric loading, are subject to implosion and virtually simultaneous explosion on sudden devacuation such as caused by breakage.

The term devacuation as used herein is intended to mean the converse of vacuation as in the case where a yacuumized vessel or tube experiences an internal pres sure change toward atmospheric upon loss of vacuum. The rate of change may occur rapidly, in which case the deleterious effects can be exceedingly violent, or more slowly over a longer period of time whereby such effects are greatly moderated. Obviously, moderating the rate of devacuation results in a gradual dissipation of the energy forces causative of destructive implosion.

The present invention provides an implosion-resistant system which is capable of being incorporated into all existing types and shapes of conventional cathode-ray picture tubes with only minor alterations or modifications of a portion of the envelope component fabricating procedures. The invention may be incorporated into any selected type of tube using materials and methods capable of supplementing normal bulb and tube production. The term bulb is applied to hollow glass envelopes having virtually none of the imageproducing electrical components installed except one or more anode buttons in the funnel sidewall. The term tube is used to designate the completed electron-discharge device having all of its electrical components installed in fully-evacuated condition capable of displaying a raster on its image-creating screen.

In a preferred embodiment of the present invention, a glass cathode-ray tube envelope 10 is normally comprised of a funnel member 11, faceplate member 12 and neck tubulation 13 which are joined to form a unitary hollow glass article capable of withstanding the loading of atmospheric pressure when vacuumized. The terminating end of neck tubulation 13 is normally sealed by an end cap 14, retaining one or more electron beam-emitting guns which project forwardly interiorly through neck tubula tion 13. Funnel member 11 is usually frusto-conical in shape in the case of cylindrical tubes, or frusto'pyramidal in the case of rectangular tubes, with its smaller end 1111 sealed to neck 13 and its larger end 11b sealed to complemental faceplate 12 at a planar seal line 15. Electromagnetic beam-deflecting coils (not shown) are normally exteriorly mounted at the yoke area where neck 13 and funnel small end 11a are joined to provide proper scanning of the tube screen 16 by the electron beam.

Faceplate 12 consists of a concavo-convex viewing portion 12a bounded by a depending annular side panel or flange 12b. Flange 12b and funnel large end 11b terminate in annular sealing surfaces of complemental configuration and planar contour. The sealing surfaces are joined at seal line 15, either by direct fusion of the glass or by an interposed annular layer of low-melting glasssealing composition such as a crystallizing-type solder glass which is selected as being compatible with the thermal and physical characteristics of the parent glass parts. The basic shape of the envelope-viewing panel 12a may be either circular or rectangular in plan as conventionally known in the art, with the sealing surfaces being substantially planar for forming a durable hermetic joint. The foregoing description is applicable to many known types of television picture tubes used for both monochromatic and polychromatic image creation, a rectangular tube being shown in FIG. 1 for illustrative purposes.

The invention as presently contemplated consists of applying selected elements to external non-viewing surfaces of the tube envelope closely adjacent its viewing area, either after a tube is fully fabricated or prior to subjecting the envelope or a bulb to a tube-fabricating process. As stated, in the former case the tube is fully completed and assembled with all its required external and internal working components properly installed in operative alignment after being subjected to bake-out temperatures and evacuation. In the latter case, the tube envelope consists of the so-called glass bulb having only a part of the electronic working components installed such as a metal anode button in the funnel sidewall and/or a plurality of masked mounting studs sealed in ternally of faceplate flange 12b for supporting a colorcontrolling aperature mask. In the case of a color TV envelope, the envelope or bulb may be subjected to the application of the required reinforcing elements with ambient conditions existing both exteriorly and interiorly thereof. The bulb, after being fabricated into a form where its devacuation can be controlled, is then subjected to a tube-fabricating process. In this case, the components of the present implosion-resistant system must be capable of withstanding required bake-out cycling ternperatures and pressures of the tube-making process.

In describing a preferred embodiment of the present invention as shown in FIGS. 1 and 2, a completed picture tube 10 capable of recreating transmitted images is subjected to reinforcement of the tube envelope in the following manner.

The concavo-convex configuration of the rectangular viewing area 12a of the faceplate 12 is shown as typical of many conventional types of cathode-ray picture tubes. The annular rim or skirt portion 12b of the rectangular faceplate has a substantially greater width at the center of its arcuately-shaped long axis sides and lesser width on its similarly-shaped short axis sides, the rim terminating in a sealing edge which resides in a fiat plane. Due to the concave-convex configuration of the viewing panel 12a merging into the rectangular shape of the skirt portion 12b, the corner areas of the faceplate 12.

have the shortest skirt dimension while the long axis sides have greatest skirt dimension. The faceplate as formed is usually made with a mold match line which extends exteriorly circumferentially parallel to the sealing edge, the mold match line being a region of maximal cross-sectional dimensions of the envelope.

It is preferred in the present invention that the mold match line he formed with a slight peripheral rib or protuberance which extends at least around the corners of the faceplate rim or preferably throughout its circumferential extent. Rib 120 as best shown in FIGS. 2 and 3, extends continuously around the exterior surface of rim portion 12b intermediate the corner radius 12d and seal line 15. The bead or rib is preferably of sutficient cross-section to provide an annular recess either forwardly or rearwardly of the mold match line to facilitate the retention of an endless reinforcing wire 18.

The wire 18 is mounted around the rim closely adjacent the mold match line in parallel relation to seal line 15. Wire 18 is comprised of a metal or metallic alloy having a coefficient of thermal expansion closely matching the parent glass of the faceplate. The wire may be fabricated having dimensions which are complemental to the exterior glass surface. One procedure involves custom-sizing the endless wire loop to the surface and then welding its ends having a prescribed undersize dimension, following which the wire is heated and then placed over the prescribed region-preferably closely rearwardly of the mold match line rib 120. An exterior layer 19 of solder glass also having a coefiicient of thermal expansion complemental to both the parent glass and metal is applied over and around the exterior surface enclosing and surrounding endless wire 18. The wire which is sealed to the exterior surface of the glass by the vitreous or crystallized solder glass layer 19 becomes an integral part of the faceplate member itself. The wire, when placed in tension, is capable of imparting compressive stresses into the glass sidewall therebeneath.

An example of the solder glass which is utilizable in the present invention is Kimble Product No. CV-130, manufactured and sold by Owens-Illinois, Inc., which sealant is a low-melting crystallizable-type sealing composition having an expansion coefficient of 90 to 104 X per degree C. and a sealing temperature range of from 430 to 450 C. for a time of about 60 minutes. Such solder glass has a density of 6.53, annealing point of 305 C., and a fiber softening point of 375 C. Also, Kimble Solder Glass 86-68, which is a vitreous-type low-melting sealing composition is adapted to use in the present invention. Such sealant has a thermal expansion coefficient of 95 to 105 X 10- per degrees C., sealing temperature of about 460 C. for about minutes under load, a density of 5.90 grams per cc., an annealing point of 348 C., and a fiber softening point of 412 C. Also Kimble Solder Glass SG-67, which is a vitreous solder glass, may be used in the present invention, such sealant having a thermal expansion of 85 to 95 X 10- per degrees C., a sealing temperature range of 440 C. for 60 minutes under load, a density of 5.38 grams per cc., an annealing point of 365 C., and a fiber softening point of 441 C. An example of the endless wire is one which is comprised of Sylvania No. 4 alloy, or No. 316 stainless steel, both of which have desirable coefiicients of thermal expansion of about 90 X 10 per degrees 0., both materials being well-known for their use in the manufacture of component metallic'parts for cathoderay picture tubes.

In the embodiment of the invention shown in FIG. 4, the single endless loop of wire is mounted forwardly of annular rib 12c in close proximity thereto. A similar layer 21 of low-melting solder glass is employed to encapsulate the wire and retain the same in place on the exterior surface of the faceplate. Such encapsulation prevents the wire from slipping forwardly during utilization of the tube and bonds the wire to the exterior surface.

In still another embodiment of the invention, FIG. 5 illustrates a pair of endless wire loops 22, one being mounted forwardly and the other being mounted rearwardly of annular rib 120. Each of the wires is placed in the re-entrant recess provided by the rib and a surrounding encapsulating layer 23 of solder glass is employed to surround and enclose both wires.

In another embodiment of the invention as shown in FIG. 6, a single endless wire loop 24 is embedded in the parent glass immediately rearwardly of mold match rib 120. A portion of the metal wire may be exposed after the sealing process without adversely affecting reinforcing results. By strengthing the rim glass sidewall in such fashion, the sidewall may be considerably strengthened. Upon fracture, cracks are not permitted to widen or propagate due to the integral reinforcement of the wire. The basic requirement is that the glass and metal be sufficiently closely matched in thermal expansion to obtain a proper glass-tometal seal.

A series of tests were conducted on 9 inch rectangular tube, a total of seven (7) samples being devacuated by impact. All tests were conducted at 5 foot-pounds impact in which the impact locations were at the most critical areas of the faceplate. The samples tested each had a construction similar to that shown in FIGS. 2 and 3. In every case, the rim glass held firmly together and the result was a large hole causing devacuation in the face without any adverse implosion-explosion effects. In each test, only one to three ounces of fine glass shale fell immediately in front of the test cabinet and no glass was thrown over three and five foot barriers set up in front of the cabinet.

Tests with one as well as more than one wire sealed onto the exterior surface of the rim glass have been conducted along with one wire being embedded into the rim. The tube size and shape are essential considerations in determining the number of wires required. In one case, a single wire was embedded into the rim glass of a round oscilloscope display tube immediately behind the faceplate radius. The wire was under no tension when it was sealed in place. Although the faceplate glass thickness was not optimum, the result of a 5 foot-pound impact was a small hole producing devacuation. Also tests have been conducted sweating one to three loops of wire onto the rims of 9 inch rectangular tubes, the wire positions ranging from immediately behind the face radius to the seal zone, although the preferred position for the reinforcement is the mold match line area immediately behind the radius of the faceplate. In some of the tests, the wire on glass surface was glazed over with a thin layer of epoxy resin rather than the solder glass referred supra. Again the 5 foot-pound impacts resulted in hole-type devacuations with good results.

We claim:

1. An essentially all-glass cathode-ray tube envelope which is resistant to fracture comprising:

a substantially funnel-shaped hollow body portion having a viewing portion enclosing its larger end and a neck tubulation projecting from its smaller end,

said viewing portion having a light-transmitting viewing panel capable of withstanding normal usage without breakage and an integral peripheral sidewall region of substantially maximum cross-sectional dimensions of said envelope,

the exterior surface of said sidewall region having a recessed area extending at least partially circumferentially normal to the envelope axis, and

at least one annular strand of metallic wire sealed within said recessed area, said strand having suf- -ficient tensile strength to retard fracture propagation through the sidewall therebeneath upon breakage of said envelope.

2. A cathode-ray picture tube envelope in accordance with claim 1, wherein said annular strand of metallic wire has a coefficient of thermal expansion complemental to the glass viewing portion and is sealed into said recessed area by a layer of low-melting solder glass.

3. A cathode-ray picture tube envelope in accordance with claim 1, wherein said annular strand of metallic wire comprises an endless ring which is complemental to and shrunk into said recessed area of said sidewall region, said recessed area being located closely adjacent said viewing panel and adapted to receive said wire ring.

4. A cathode-ray tube envelope in accordance with claim 1, wherein said recessed area extends fully circumferentially of said viewing portion sidewall region at the mold match line normal to the tube axis.

5. A cathode-ray tube envelope in accordance with claim 1, wherein said annular strand of metallic wire is comprised of stainless steel alloy having a coefficient of thermal expansion closely complemental to said glass viewing portions, said strand being in tension to impart compressive stresses into the glass sidewall region therebeneath.

6. A cathode-ray tube envelope in accordance with claim 1, wherein said annular strand of metallic wire is sealed into the said recessed area in partially embedded bonded relation forming a glass-to-metal annular seal.

7. An essentially all-glass cathode-ray tube envelope which is resistant to fracture and implosion-explosion effects upon breakage comprising:

a substantially funnel-shaped hollow body portion having a viewing portion enclosing its larger end and a neck tubulation projecting from its smaller end,

said viewing portion having a light-transmitting viewing panel capable of withstanding a five foot-pound impact without breakage and an integral peripheral sidewall region having a planar mold match line of substantially maximum cross-sectional dimensions of said envelope,

the exterior surface of said sidewall region having an annular recess extending at least partially circumferentially normal to the tube axis and formed closely adjacent said viewing panel, and

at least one annular strand of metallic wire permanently bonded within said annular recess by an annular layer of low-melting crystallizing-type solder glass, said strand and annular layer of sealant having coefficients of thermal expansion complemental to the glass viewing portion and sufficient tensile strength to retard fracture propagation through the sidewall therebeneath upon breakage of said envelope.

8. The method of protecting an essentially all-glass cathode-ray tube envelope against fracture and implosiveexplosive effects upon breakage comprising the steps of:

forming the viewing portion having a light-transmitting viewing panel capable of withstanding normal usage without breakage and an integral peripheral sidewall region with an annular protuberance adjacent the mold match line thereby providing an annular recess, mounting at least one annular strand of metallic wire within said recess adjacent said mold match line, and sealing said metallic wire within said recess by an annular layer of low-melting solder glass, said wire and said solder glass having coefficients of thermal expansion complemental to said glass viewing portion, said sealed in strand having suificient tensile strength to retard fracture propagation through the sidewall therebeneath upon breakage of said envelope.

9. The method of protecting an essentially all-glass cathode-ray tube envelope against fracture and implosiveexplosive eifects upon breakage comprising the steps of:

forming the viewing portion of glass having a lighttransmitting viewing panel capable of withstanding normal usage without breakage and an integral peripheral sidewall region with an annular recess extending at least partially circumferentially adjacent the mold match line, and

embedding at least one annular strand of metallic wire within the peripheral sidewall region of the glass viewing portion, said wire and parent glass having complemental COfifl'lCiflntS of thermal expansion.

References Cited UNITED STATES PATENTS MARTHA L. RICE, Primary Examiner US. Cl. X.R. -43, 59 

